Along with the evolution of community and the rise of people's living standard, the requirements on comfort and safety stability of the car riding are getting higher and higher. Active suspension system gets more attention as an important part of modern cars, because it has a very important influence on the riding stability and reliability. Meanwhile, the researches of tubular linear motor are drawn more attention as the key component of active suspension system. Furthermore, the fault-tolerant performance of the motor with short-circuit faults directly determines the reliability of electromagnetic suspension and the ability of continuous operation.
When fault-tolerant motor is with one or two short-circuit phase faults, the motor can still have a certain thrust force or torque output capability. However, the higher thrust force or torque fluctuation and noise seriously deteriorate the system performance. The aim of Fault-tolerant control is to optimize the fault-tolerant currents according to different operation condition, and to make the output thrust force or torque of the motor smooth as much possible as it can, thus having nearly the same performance as that under healthy condition. The application number of China's invention patent is 201510059387.2—“A short-circuit fault-tolerant control method for five-phase fault-tolerant permanent-magnet motor”. To achieve the smooth operation of the five-phase fault-tolerant surface-mounted permanent magnet rotary motor, the impact of the short-circuit faults on the torque was divided into two parts. Part one is the impact of the open-circuit phase fault on torque, and the other part is the impact of short-circuit phase current on torque. The principle of constant magnetic motive force (MMF) before and after fault and the principle of equal amplitude of the phase currents after fault are used to optimize the phase currents of the remaining healthy phases. Meanwhile, to restrain the torque fluctuation caused by short-circuit currents, the healthy phase compensation currents are calculated based on the principle that post-fault MMF is zero and the minimum copper loss. Then, the current references of remaining healthy phases can be obtained by adding the two above mentioned currents. According to the obtained remaining healthy phase currents, the current hysteresis loop control strategy was adopted to control the five-phase fault-tolerant permanent-magnet rotary surface-mount motor. In this method, the amplitude of the remaining healthy phase compensation currents which used to restrain torque fluctuation caused by short-circuit phase currents is constant, and it has nothing to do with the motor speed. Meanwhile, the sum of remaining healthy phase currents is not zero. And also it is not suitable for fault-tolerant operation in the case of two phase faults (open-circuit phase faults; short-circuit phase faults; one open-circuit phase fault and the other short-circuit phase fault). At present, the common fault-tolerant control methods are to calculate the fault-tolerant currents, and then adopt the current hysteresis loop strategy to control motor. However, these methods have the problems about chaotic switching frequency, large noise and poor dynamic performance. So these methods are not suitable for motor with high power and high requirement on dynamic performance. The application number of China's invention patent is 201510661212.9—“A short-circuit fault-tolerant field-oriented control method of fault-tolerant tubular linear motor with interior hybrid magnetic materials”. To accomplish the fault-tolerant operation of the five-phase fault-tolerant tubular linear motor with interior hybrid magnetic materials, which is with one short-circuit phase fault, the same method as mentioned above was used to optimize the remaining healthy currents, then the field-oriented control strategy was adopted to achieve the motor's field-oriented operation under one short-circuit phase fault. Although this method achieves the high fault-tolerant performance, high dynamic performance and good current tracking performance of the motor system with short-circuit faults, but this method cannot achieve fault-tolerant operation under two phase faults (open-circuit phase faults; short-circuit phase faults; or one open-circuit phase fault and the other short-circuit phase fault).